Wellbore fluid treatments such as fracing are sometimes effected through tubular strings including ported tubulars. In some cases, it is useful to run the ported tubular in a port closed condition and open the ports when the tubular is in position in the wellbore. For this purpose, valves may be provided for the ports to allow selective opening of the ports.
In some tubulars, a hydraulically openable sleeve valve is provided and positioned to act over one or more ports. The sleeve valve is axially slidable along the tubular from a position covering and closing the ports over which it is disposed to act to a position where it is retracted from and opens the ports. The sleeve valve includes a piston face that may be acted upon by hydraulic pressure, controlled from surface, in order to move the sleeve. The sleeve may act in the inner bore of the tubular to move along the inner wall surface or the sleeve may act along the outer surface of the tubular. Shear screws, also termed shear pins, may be used to hold the sleeve valve in the port closed position until sufficient pressures are encountered to overcome the holding capabilities of the shear screws to move the sleeve.
In ported tubulars that include hydraulically driven sliding sleeve valves for opening ports therein, there is a lot of reliance on shear pin stock. The shear pins are selected to fail at a particular shear pressure, as applied by hydraulic pressure acting on the sleeve, and if the shear pin rating is erroneously indicated, if the shear pins are defective or if more screws than called for in any design are used, the sleeve may not be released, leaving the ports of that tubular sub unopened. A similar problem may occur where the sliding sleeve becomes jammed by debris or damage.